Finding: ‘El Niños 10,000 years ago were as strong and frequent as the ones we experience today’

The planet’s largest and most powerful driver of climate changes from one year to the next, the El Niño Southern Oscillation in the tropical Pacific Ocean, was widely thought to have been weaker in ancient times because of a different configuration of the Earth’s orbit. But scientists analyzing 25-foot piles of ancient shells have found that the El Niños 10,000 years ago were as strong and frequent as the ones we experience today.

The results, from the University of Washington and University of Montpellier, question how well computer models can reproduce historical El Niño cycles, or predict how they could change under future climates. The paper is now online and will appear in an upcoming issue of Science.

“We thought we understood what influences the El Niño mode of climate variation, and we’ve been able to show that we actually don’t understand it very well,” said Julian Sachs, a UW professor of oceanography.

The ancient shellfish feasts also upend a widely held interpretation of past climate.

“Our data contradicts the hypothesis that El Niño activity was very reduced 10,000 years ago, and then slowly increased since then,” said first author Matthieu Carré, who did the research as a UW postdoctoral researcher and now holds a faculty position at the University of Montpellier in France.

In 2007, while at the UW-based Joint Institute for the Study of the Atmosphere and Ocean, Carré accompanied archaeologists to seven sites in coastal Peru. Together they sampled 25-foot-tall piles of shells from Mesodesma donacium clams eaten and then discarded over centuries into piles that archaeologists call middens.

While in graduate school, Carré had developed a technique to analyze shell layers to get ocean temperatures, using carbon dating of charcoal from fires to get the year, and the ratio of oxygen isotopes in the growth layers to get the water temperatures as the shell was forming.

The shells provide 1- to 3-year-long records of monthly temperature of the Pacific Ocean along the coast of Peru. Combining layers of shells from each site gives water temperatures for intervals spanning 100 to 1,000 years during the past 10,000 years.

The middens are ancient dumping sites that typically contain a mix of mollusk shells, fish and bird bones, ceramics, cloth, charcoal, maize and other plants.

The new record shows that 10,000 years ago the El Niño cycles were strong, contradicting the current leading interpretations. Roughly 7,000 years ago the shells show a shift to the central Pacific of the most severe El Niño impacts, followed by a lull in the strength and occurrence of El Niño from about 6,000 to 4,000 years ago.

One possible explanation for the surprising finding of a strong El Niño 10,000 years ago was that some other factor was compensating for the dampening effect expected from cyclical changes in Earth’s orbit around the sun during that period.

“The best candidate is the polar ice sheet, which was melting very fast in this period and may have increased El Niño activity by changing ocean currents,” Carré said.

Around 6,000 years ago most of the ice age floes would have finished melting, so the effect of Earth’s orbital geometry might have taken over then to cause the period of weak El Niños.

In previous studies, warm-water shells and evidence of flooding in Andean lakes had been interpreted as signs of a much weaker El Niño around 10,000 years ago.

The new data is more reliable, Carré said, for three reasons: the Peruvian coast is strongly affected by El Niño; the shells record ocean temperature, which is the most important parameter for the El Niño cycles; and the ability to record seasonal changes, the timescale at which El Niño can be observed.

“Climate models and a variety of datasets had concluded that El Niños were essentially nonexistent, did not occur, before 6,000 to 8,000 years ago,” Sachs said. “Our results very clearly show that this is not the case, and suggest that current understanding of the El Niño system is incomplete.”

The research was funded by the U.S. National Science Foundation, the U.S. National Oceanic and Atmospheric Administration and the French National Research Agency.

Other co-authors are Sara Purca at the Marine Institute of Peru; Andrew Schauer, a UW research scientist in Earth and space sciences; Pascale Braconnot at France’s Climate and Environment Sciences Laboratory; Rommel Angeles Falcón at Peru’s Minister of Culture; and Michèle Julien and Danièle Lavallée at France’s René Ginouvès Institute for Archaeology and Anthropology.

76 thoughts on “Finding: ‘El Niños 10,000 years ago were as strong and frequent as the ones we experience today’”

Slowly but surely the truth is coming out about how untrustworthy the computer models used by climate scientist are, compared to real empirical data. CO2 alarmist’s are losing their minds over this & I take great enjoyment in watching them try to explain their point of view.

“Climate models and a variety of datasets had concluded that El Niños were essentially nonexistent, did not occur, before 6,000 to 8,000 years ago,” Sachs said. “Our results very clearly show that this is not the case, and suggest that current understanding of the El Niño system is incomplete.”

First line in the abstract: “Understanding the response of the El Niño-Southern Oscillation (ENSO) to global warming requires quantitative data on ENSO under different climate regimes” They just had to say it. It’s probably a requirement to frame things relative to global warming to get published….

I appreciate their hard work but nobody has ever had a clue about what causes changes in ENSO.
Every prediction of it they make more than 3 months out fails miserably yet they’re surprised computer models don’t know what it was like 10,000 years ago?

Are all these new studies coming out because a new generation has taken over and the corrupt ones like Hansen, Mann, Briffa, Jones are aging towards retirement? Will history look back and show that 25 year span starting in 1988 for what it was ‘A time when a group of scientists led by Hansen and Mann decided to distort and adjust facts to meet a political agenda’. Are hurricanes up? Are tornadoes up? Mosher and Stokes know deep down that CAGW is a myth and the slight warming we have gotten is mostly beneficial.

The El Niño/Southern Oscillation (ENSO) phenomenon is believed to have operated continuously over the last glacial–interglacial cycle1. ENSO variability has been suggested to be linked to millennial-scale oscillations in North Atlantic climate during that time2, 3, but the proposals disagree on whether increased frequency of El Niño events, the warm phase of ENSO, was linked to North Atlantic warm or cold periods. Here we present a high-resolution record of surface moisture, based on the degree of peat humification and the ratio of sedges to grass, from northern Queensland, Australia, covering the past 45,000 yr. We observe millennial-scale dry periods, indicating periods of frequent El Niño events (summer precipitation declines in El Niño years in northeastern Australia). We find that these dry periods are correlated to the Dansgaard–Oeschger events—millennial-scale warm events in the North Atlantic climate record—although no direct atmospheric connection from the North Atlantic to our site can be invoked. Additionally, we find climatic cycles at a semiprecessional timescale (approx11,900 yr). We suggest that climate variations in the tropical Pacific Ocean on millennial as well as orbital timescales, which determined precipitation in northeastern Australia, also exerted an influence on North Atlantic climate through atmospheric and oceanic teleconnections.

…..Our results show that the ENSO system has the potential for more extreme variability than that observed in the modern instrumental record. The reduced El Niño frequency and amplitude during the mid-Holocene, and a shift to strong El Niño events at 2.5-1.7 ka, is similar to the pattern observed in modeling and paleo-lake studies. However, the coral records for 2.5–1.7 ka show evidence for El Niño events more severe than the 1997-1998 event, and longer than the multi-year 1991–1994 event……
Geophysical Research Letters Vol 31, L11204,
doi:10.1029/2004GL019972http://business.uow.edu.au/sydney-bschool/content/groups/public/@web/@sci/@eesc/documents/doc/uow057057.pdf
———————

Abstract – August 2000
Thierry Corrège et alEvidence for stronger El Niño-Southern Oscillation (ENSO) Events in a Mid-Holocene massive coral
We present a 47-year-long record of sea surface temperature (SST) derived from Sr/Ca and U/Ca analysis of a massive Porites coral which grew at ~ 4150 calendar years before present (B.P.) in Vanuatu (southwest tropical Pacific Ocean). Mean SST is similar in both the modern instrumental record and paleorecord, and both exhibit El Niño-Southern Oscillation (ENSO) frequency SST oscillations. However, several strong decadal-frequency cooling events and a marked modulation of the seasonal SST cycle, with power at both ENSO and decadal frequencies, are observed in the paleorecord, which are unprecedented in the modern record.
Paleoceanography – Volume 15, Issue 4, pages 465–470, August 2000http://tinyurl.com/ob443sz
———————

Nature Article – March 2003
Kim M. Cobb et al
El Niño/Southern Oscillation and tropical Pacific climate during the last millennium
…..The most intense ENSO activity within the reconstruction occurred during the mid-seventeenth century. Taken together, the coral data imply that the majority of ENSO variability over the last millennium may have arisen from dynamics internal to the ENSO system itself.http://www.nature.com/nature/journal/v424/n6946/abs/nature01779.html

———————

Abstract – 11 Sep 2004
Bert Rein et alA major Holocene ENSO anomaly during the Medieval period
Here, we present a high resolution marine El Niño flood record from Peru. A period of extreme drought without strong flooding occurred from A.D. 800–1250. Anomalous precipitation patterns characterized the entire Indo-Pacific ENSO domain, with dry events in the northern Arabian Sea and the mid-latitudes of both Americas, coinciding with wet periods in the Atlantic Cariaco Basin…..
Geophysical Research Letters – Volume 31, Issue 17, September 2004
DOI: 10.1029/2004GL020161

CAGW is clearly understood. AGW is warming of 0 degrees to 1.99 C. CAGW is 2.0 or higher. Life on earth will end if the temp. goes up 2C. Ebola most likely will kill all the humans before the plankton dying kills the rest of life on earth.

[It is very telling of today’s headlines, and today’s CAGW supporters, that we do not know (and cannot tell) if this paragraph needs a “/sarcasm” tag added. .mod]

If it’s not catastrophic then who gives a toss? The EU supposes to reduce CO2e emissions 80% by 2030 compared to 1990. That would be a catastrophe – considering agriculture alone makes up most of the remaining 20%.

If it’s just AGW and not CatastrophicAGW then a whole lot of feeble-minded “scientists” are on the dole.

A nice piece of science, putting together two separately recognized established methods (radiocarbon dating from archeology and delta O13 from climatology ice cores and ocean proxies) to actually go analyze real middens (which exist, cause he has pictures) and can be resampled for reproducibility (which he already did, and anyone else could). Low and behold, ENSO is not new news. The only stunning part is that warmunists supposed it might have been in order to perpetuate their hockey stick world view.
Well, upon further reflection, how could anyone be stunned by anything that warmunists have ever espoused, since it is almost all beyond silly? As proven yet again here.

“According to Fig. 5, a series of intense El Nino events (high red color intensity) begins at about 1450 BC that will last for centuries. In that period normal (La Nina) conditions have but disappeared. For comparison, the very strong 1998 El Nino event scores 89 in red color intensity. During the time when the Minoans were fading, El Nino events reach values in red color intensity over 200.”http://www.clim-past.net/6/525/2010/cp-6-525-2010.pdf

CAGW is clearly understood. AGW is warming of 0 degrees to 1.99 C. CAGW is 2.0 or higher. Life on earth will end if the temp. goes up 2C. Ebola most likely will kill all the humans before the plankton dying kills the rest of life on earth.”

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Actually, not it depends. of course you’ll find in the non scientific alarmist literature references to some effects that would be catastrophic at 3C, but in the science.. there isnt a well defined concept known as a “catastrophe”

I quote: “…scientists analyzing 25-foot piles of ancient shells have found that the El Niños 10,000 years ago were as strong and frequent as the ones we experience today. The results, from the University of Washington and University of Montpellier, question how well computer models can reproduce historical El Niño cycles…”

And well they might question because these modelers don’t have the faintest idea of what El Nino is or how it got started in the first place.. Comes from not doing your homework because it is all there in my book “What Warming?” First, El Nino is part of ENSO, an harmonic oscillation of equatorial Pacific water from east to west. It has a natural period of about 5 years but oceanic conditions can shorten or lengthen it at times. Trade winds pile up the warm water into the Indo-Pacific Warm Pool, and the Pacific Warm Pool as well. When the water level in the Indo-Pacific Warm Pool is high enough reverse gravity flow starts. An El Nino wave forms, follows the equatorial countercurrent, runs ashore in South America, spreads out along the coast, and warms the air above it. Rising warm air interferes with trade winds, joins the westerlies, and we notice that an El Nino has arrived. But any wave that runs ashore must also retreat. When the El Nino wave retreats the water level behind it drops by half a meter, cold water from below wells up, and a La Nina has started. As much as the El Nino warmed the air the La Nina will now cool it and the global mean temperature is not changed. This has been going on as long as the present configuration of equatorial Pacific currents has existed, which is to day since the Panamaian Seaway closed. That is about two million years, far more than the ten thousand they have just discovered.

I believe anthropologists studying ancient Andean cultures have linked major periods of civil disruption and abandonment of ancient cities to periodic super El Niño events going back more than 5,000 yrs before present. Of course they might be looking to the possibility of such events as cultural drivers when other factors may have been the true cause.

GCMs are entirely fictitious. They don’t use actual data. They make assumptions straight down the line, about future CO2 levels, feedbacks, clouds, everything. They’re GIGO from the git-go. No wonder they have failed utterly to forecast, since they can’t even hindcast, having never been validated.

But to make it truly valid, it must also be shown the La Ninas were also as strong and frequent.

Then for it to be a possible challenge to the global climate models, it must be shown El Ninos and La Ninas had global effects back then comparable to what current ones yield. What proof is there they weren’t just regional effects? Without it, you might as well try showing rampant global warming from a single distressed tree in Yamal. Who would believe that?

Lewis P Buckingham says:
August 8, 2014 at 8:28 pm
How do we know that shells are a good proxy for temperature?
>>>>>>>>>>>>>

Completely different approach from tree rings:

While in graduate school, Carré had developed a technique to analyze shell layers to get ocean temperatures, using carbon dating of charcoal from fires to get the year, and the ratio of oxygen isotopes in the growth layers to get the water temperatures as the shell was forming.

Not that this makes in infallible, but the technique is credible as the oxygen isotopes are known to vary with temperature. Tree rings on the other hand vary with temperature, precipitation, length of growing season, disease, insect infestation, competition from other trees, soil fertility (including if or when a bear when poop and where) and so on. Tree rings are a joke.

kadaka said Then for it to be a possible challenge to the global climate models, it must be shown El Ninos and La Ninas had global effects back then comparable to what current ones yield. What proof is there they weren’t just regional effects?

You must be blind or undereducated for your present position. The proof been out there found in geological and archaeological studies(mainly underwater archaeologic studies of settlements from todays English channel over the North Sea all way up to close to island studies in Alta region, Norway). Studies of settlements that within a short period(50 to 100 years) had to be abondoned.

You seem to be unaware of what happened. Here in Scandinavia every pupil of 12 should have heard of it in school. When a hugh amount of fresh water within days “slipped” into the ancient Atlantic’s salt water system it caused a tremendous sudden effect on sea streams, straiths and during a short period (same 50 to 100 years) the collision between non-salt cold water with high saltination straiths, some warm (up to 24/25 degrees Celcius) some less warm but with high saltination factor caused phenomena such as El Nino, La Ninas etc. around the globe to “occure”.

That’s easy to take into computer models had some of all the so called AWG believers who wrote what they call models taken the 43 most essential factors for sealevel calculation in the past. I had it in my C-essay back in -93. Oh you must of course know exactly when and why it all happened and have knowledge of what type of sediment/ground/soil analyses you need to prove the effect around the globe for. But you don’t seem to know. Do you?

Well what happened happened 11 500 years ago. Within a short time, 50 years the temperature over Northern Hemisphere tised 12 degrees Celsius causing among other things a large lake called Yoldia Sea to fill up in and over the land as well as sea area of today’s Baltic Sea. When the inland sea (that was what it was/had been for aproximate 600 years) emptied over land within 50 years 10 700 BP causing a quick landrise of 25 meters around the Baltic Sea was followed by the Ancylus sea/lake with even colder and less salt water than the Yoldia Sea had had.

Short before 10 000 BP the Ancylus sea broke way over newly landrised land. The place that in earlier days was belived to be the place where erosion caused the sea to brake thru to the Atlantic area is called Sveafallet. Today’s scientists specialisted in studying sediment and how to date them places the exact location west of today’s Lake Vaenern (at that time part of the Ancylus Sea). If you had known where to look for the special geologic studies you should have needed to be able to make models, I had worked two summers in my youth for the geologic dept of a Swedish firm almost dominating the world for that type of analyses, you should have been able to put these factors together with chemical formulas for what happens in open sea when cold straights meet warm and if you had you would have known that the Earth rotation, wobbling and effect of sun on warm sea (with over 27 degrees Celcius temperature) caused effects not only locally but all around the Northern Hemisphere.

It’s basic knowledge of University Mathematic that’s all one need for finding the answer. The answers have to be checked for each 1000 meter around the coasts of today in Northern parts of Northern Hemisphere. In other words matematic variables gives figures which you have to check using empiric knowledge around the Atlantic and the Pacific Ocean. Then you will find where phenomena like El nino can and probably will occure. If you have matematic variables for saltination distribution combined with variables for temperature over seasons for each studied “point” you also will find almost all factors needed to understand El nino variations.

All this is simple to understand. But of course you need to know where to look for empiric data to prove thesis in each “GSP”-point you study.

Mosher does not even know what an El Nino is meteorologically… It is a distortion of the boreal hemisphere circulation, so there are no reasons that this event would not have happened in the past, especially given the known climatic shifts (glaciations/deglaciations).

Interesting results. Some years ago, I plotted up the raw oxygen isotope data measured by Stuiver and Grootes (1997) from the GISP2 ice core and was surprised to find 40 recurring warm/cool periods since 1480 AD. The average of each warm or cool cycle was 27 years, essentially the same as the PDO (http://www.nipccreport.org/reports/ccr2a/pdf/Chapter-5-Cryosphere.pdf
Figure 5.9.6.3, page 689. I’ll plot up the rest of the data and compare it with the data of Carre et al.

New data shows modern El Ninos are the same intensity/severity as they were 10,000 years ago… and the best ‘climate models’ don’t emulate this at all. The ‘climate models’ are shown to be significantly in error, yet again. GIGO.

no one of serious thought doubts that 3.5C rise wouldn’t have many many serious negative consequences for mankind.

but how do we have any control over that when CO2 sensitivity is likely ~1deg C? 285 ppm x 2^3.5 = 3220 ppm. If man’s total combustion of fossil fuels to date is an additional 120ppm CO2, we run out of all fossil carbon sources before we get to 1800 ppm. And that in at least 250 years from now.

oh yeah, it GCMs all the way down. silly me. It’s more likely in 200 years from now they’ll be thanking us from saving the world from the next Glacial cycle.

ENSO, AMO, etc.exist.
They are cyclical and we have absolutely not the vaguest idea if they are slowly ramping up or down because we lack the necessary multi-centennial observation data. Models that take them into account are not verifiable, therefore will not be validated for many generations to come.

Short term variations of the atmospheric temperature are linked to such cycles, but long term climate changes have nothing to do with them – multi-decadal is very short term in climate speak.

There’s actually been little discussion about this paper in comments so far.

Unfortunately it’s paywalled and we don’t get to see any of the data, graphs, or anything to assess the validity of the study.

If I understand the description, these are large dumps of shellfish remains caught, cooked and dumped. The dating comes, not from depth position ( which would be useless in this context ) but from carbon remains from the fire that cooked each sample.

Now you need to paper to see how they get samples that are not affected by cross-contamination.

The main problem I see is that C14 dating is not very accurate and is very sensitive to individual measure errors and calibration.

http://en.wikipedia.org/wiki/Radiocarbon_dating#Errors_and_reliability
Radiocarbon dates are generally presented with a range of one standard deviation (usually represented by the Greek letter sigma: σ) on either side of the mean. This obscures the fact that the true age of the object being measured may lie outside the range of dates quoted. In 1970, the British Museum radiocarbon laboratory ran weekly measurements on the same sample for six months. The results varied widely (though consistently with a normal distribution of errors in the measurements), and included multiple date ranges (of 1σ confidence) that did not overlap with each other. The extreme measurements included one with a maximum age of under 4,400 years, and another with a minimum age of over 4,500 years.[57]

How it is possible pick up variations on an inter-annual scale using dating with that kind of impression needs to be looked at very carefully.

On the face of it, it seems highly questionable.

Until I get to see how and whether they address this issues in the paper I won’t be regarding it as anything more substantial.

All living proxies are simply a good proxy for the environmental conditions in general in which the proxy finds itself. Beneficial environmental conditions promotes growth, adverse environmental conditions stunt growth. Environmental conditions extend to cover extraneous factors such as competion and predators, so is wider that your list.

One cannot isolate any one specific criteria from the more general. All we can say is that at time X, it was very good, or good, or not so good, or poor, or bad, or very bad for the proxy. Why that is so, we can only speculate.

All proxy evidenc e carries with it huge error bars and should be taken with pinch of salt.

Oxygen isotopes from 25 foot piles of shells that are mixed with charcoal from fires that is carbon dated. It’s proxy on top of proxy on top of proxy and we’re expected to believe that the ‘signal’ relates to tiny changes in ocean temperatures from 10000 years ago.

The only sensible part of this is obvious – “we’ve been able to show that we actually don’t understand it very well” – now there’s a surprise.

I don’t care whether the output supports a sceptical viewpoint or an alarmist viewpoint, it’s nonsense to use proxies for anything other than a vague interpretation of anything. Because in reality you can’t possible know all the contributing factors.

This type of ‘science’ is the equivalent of Jazz (aka musical w@nking), fun for those taking part and maybe a few interested voyeurs, but contributing nothing to society as a whole.

Steve Mosher makes an important point:
The world is held in thrall by a non-defined, and therefor non-falsfiable pile of crap.
The promoters make careers and fortunes off of hyping something that is undefined.
The politicians tax and regulate and call names based on something that is not defined.
*That*, however is a pretty good definition of *scam*.

no one of serious thought doubts that 3.5C rise wouldn’t have many many serious negative consequences for mankind.
=========================
I serious doubt that it would have more negative consequences than positive. Every morning of every day temperature rises more than 3.5C where I live. The same is likely true for most people.

Humans are better adapted to warm than any other large mammal. 99% of the places where human beings live today are TOO COLD for an unprotected human to survive.

We have minimal fur, and our upright poster minimizes exposure to the sun and maximizes evaporation and cooling. Without technology (fire) we would still be living in the tropical jungles.

Warming will most certainly lead to increased food supply and increased rainfall, on average. There will be winners and losers for sure. But since most of the warming will take place in regions that are currently cold, on balance it will be largely positive.

From a technology point of view, it is much cheaper to cool an object than to warm it. All that you need for cooling is the evaporation of water. However, to heat an object requires an energy source such as fossil fuel. Water is much cheaper than fossil fuel.

Well, something has changed in Peru. The guy in the picture, standing on top of a huge midden, is surrounded by … nothing. Why have all the Peruvians left the area that was once, for many centuries, a good place to eat?

*lemiere jacques August 9, 2014 at 12:55 am says: “what i don’t undestand is the reason why they could think el nino phenomenon is more or less understood….????”
Quite so. All those “experts” know nothing about it. The reason is that the only true explanation is in my book “What Warming?” and these pseudo-scientists are too lazy to read scientific literature in their own field. Same about Arctic warming. I proved that it is not caused by the greenhouse effect but is produced by warm Gulf Stream water carried into the Arctic Ocean by currents. It was in my book and also in a journal article I wrote that you can download from Judith Curry’s blog. But these pseudo-scientists ignore it and keep babbling about global warming in the Arctic. And then they are puzzled why the Antarctic is cold and the Arctic is warming. It is very simple: if it wasn’t for the warm water carried into the Arctic by currents the Arctic would be just as cold now as the Antarctic is. If you want to know about the climate your best bet is to start with my book and ignore these blowhards.

Unlike the beginning of glacial eras or glacial /interglacial oscillations within these eras, at least the oscillation period el Niño probably is influenced by continental configuration.

Milankovitch holds one seat on the board of directors for glacial/interglacial oscillations (out of maybe 10).

Had no idea models believed ninos did not exist at the beginning of the current interglacial. Why would anyone think this? Because CO2 was low? Haha. Of course, CO2 causes el ninos, along with war, Ebola and famine.

In January 2013 Kim Cobb at UCSD published in SCIENCE a study of corals going back 7000 years. In that journal it was all about meme format, but her data revealed that the strongest ninos during that 7000 year period were during the little ice age…

ENSO is the heart of the Pacific ocean pumping equatorial heat poleward. Not surprising that it has operated throughout the Holocene. A more interesting question would be if and at what strength it operated during deep glacial periods.

gymnosperm, could the strong El Ninos noted during the LIA be the result of volcanic interruption of Walker Cells? When these cells are working, there are sufficient pressure differences between East and West oceanic areas to set up a trade wind circulation that keeps El Nino in neutral to La Nina territory (IE surface winds are blowing from East to West, keeping clouds and the solar warmed pool on the West side of equatorial ocean areas. When these cell functions are disrupted (as they have been reported to in the literature related to equatorial volcanic events), and Walker Cell pressure differences become more equal, an El Nino is triggered, the ocean surface calms, and the top layers of the ocean become defined with less mixing, setting up evaporation of the top most layer.

I am skeptical about the procedure as a whole and whether it is a representative ENSO metric. El Nino occurs three to six months every four to six years. It takes quite a bit of skills to segregate shells and examine infinitesimal shell thickness to locate temperature rise fingerprint. I question the results altogether.

ENSO increasing trend is observed at this time and noted in the IPCC Fourth assessment Report. It is the present time and we know it is increasing.